Why some companies prefer to calculate the acid-test ratio instead of current ratio?

Companies tends to calculate Acid-test ratio when they are not sure how quickly they can convert  inventories into cash or cash equivalents. therefore Acid-test ratio gives more reliable and conservative measure of the liquidity   

some companies prefer that because : *The acid_test ratio is a strong indicator of whether a company has sufficient short term asset to cover immediate liabilities. -It is known the quick ratio. -The higher the ratio ,the more financially secure a company is in the short term -A common rule is that companies with a Acid-Test or quick ratio of greater than 1. are sufficiently able to meet their short - term liabilities

To test the ability of the company to pay short term obligations by removing inventory. Inventory take long  before it can be sold. This is excluded. By simply looking at receivables and cash the company can  test its liquidity.